4.4 Taking Configuration Actions

`configure' is designed so that it appears to do everything itself, but there is actually a hidden slave: `config.status'. `configure' is in charge of examining your system, but it is `config.status' that actually takes the proper actions based on the results of `configure'. The most typical task of `config.status' is to instantiate files.

This section describes the common behavior of the four standard instantiating macros: AC_CONFIG_FILES, AC_CONFIG_HEADERS, AC_CONFIG_COMMANDS and AC_CONFIG_LINKS. They all have this prototype:

AC_CONFIG_FOOS(tag..., [commands], [init-cmds])

where the arguments are:

tag...

A whitespace-separated list of tags, which are typically the names of the files to instantiate.

commands

Shell commands output literally into `config.status', and associated with a tag that the user can use to tell `config.status' which the commands to run. The commands are run each time a tag request is given to `config.status'; typically, each time the file `tag' is created.

init-cmds

Shell commands output unquoted near the beginning of `config.status', and executed each time `config.status' runs (regardless of the tag). Because they are unquoted, for example, `$var' will be output as the value of var. init-cmds is typically used by `configure' to give `config.status' some variables it needs to run the commands.

All these macros can be called multiple times, with different tags, of course!

You are encouraged to use literals as tags. In particular, you should avoid

... && my_foos="$my_foos fooo" ... && my_foos="$my_foos foooo" AC_CONFIG_FOOS($my_foos)

and use this instead:

... && AC_CONFIG_FOOS(fooo) ... && AC_CONFIG_FOOS(foooo)

The macro AC_CONFIG_FILES and AC_CONFIG_HEADERS use specials tags: they may have the form `output' or `output:inputs'. The file output is instantiated from its templates, inputs if specified, defaulting to `output.in'.

For instance `AC_CONFIG_FILES(Makefile:boiler/top.mk:boiler/bot.mk)' asks for the creation of `Makefile' that will be the expansion of the output variables in the concatenation of `boiler/top.mk' and `boiler/bot.mk'.

The special value `-' might be used to denote the standard output when used in output, or the standard input when used in the inputs. You most probably don't need to use this in `configure.ac', but it is convenient when using the command line interface of `./config.status', see 14. Recreating a Configuration, for more details.

The inputs may be absolute or relative filenames. In the latter case they are first looked for in the build tree, and then in the source tree.